U.S. has quietest two-year period for tornadoes since 1980s – ‘Lack of landfalling tropical storms & hurricanes — which can spawn tornadoes — has also been a factor’

'The USA has had two consecutive below-average years for tornadoes, a break for a nation that typically sees more twisters than any country on Earth. one of the calmest years for tornadoes in more than two decades, according to data from the Storm Prediction Center in Norman, Okla...So far this year, through the end of October, there have been about 800 reports of tornadoes, Carbin said. In a typical full year, based on data from 1993 to 2012, the USA has more than 1,250 twisters...Since 1990, the only other year that was quieter than this year was 2002, when only 741 tornadoes were reported from January-October. The year of 2012 was also a below-average season, as only 878 tornadoes had formed by this point in the year.' -- 'The U.S. experiences about 80% to 90% of all of the tornadoes that occur across the world'